The present invention relates to methods of nanometer-scale deposition and/or depletion of nanostructures in liquids at ambient temperature and neutral pH, and more particularly to such methods that involve electric field-directed, programmable, pulsed electrolytic metal deposition and/or depletion with precise control for nanofabrication.
It has been demonstrated that hexachloroplatinate ([PtCl6]2xe2x88x92) and hexachloroosmiate ([OsCl6]2xe2x88x92) can be photoconverted to metallic platinum and osmium at the reducing site of Photosystem I (PSI) in thylakoid membranes via the Hill reaction, as shown in FIG. 1. In the search for additional compounds that can be used for photodeposition of metallocatalysts at the reducing site of PSI in thylakoid membranes, various selected compounds were assayed by simultaneously measuring H2 and O2 production in a helium atmosphere using a reactor-flow detection system. In addition to confirmation of earlier findings with [PtCl6]2xe2x88x92 and [OsCl6]2xe2x88x92, it was found that PtCl4, OSCl3, (NH4) 2RuCl6, and K3RuCl6 can also support simultaneous H2 and O2 photoevolution after photoprecipitation. For further information, see James W. Lee, et al., Molecular Ionic Probes: A New Class of Hill Reagents and Their Potential for Nanofabrication and Biometallocatalysis, J. Phys. Chem. B, 1998, vol. 102, p. 1095-2100.
Research has demonstrated that the growth of metallic particles can be controlled by photosynthetic reactions. Using single-turnover flashes, atom-by-atom growth of metallic platinum has been previously achieved. The size of metallic platinum particles grown at the reducing site of PSI can be determined by the number of actinic flashes.
In the development and/or manufacture of nanometer devices, it is often essential to have convenient and cost-effective methods for manipulating the size of a nanometer gap, for adding and/or deleting an additional metal species at the gap, and/or connecting nanostructures at a precise location. The present invention uses the foundation laid by the above-described research to achieve these goals.
Accordingly, objects of the present invention include: convenient and cost-effective methods for manipulating the size of a nanometer gap, depositing and/or depleting an additional metal species at the gap, and/or connecting nanostructures at a precise location. Further and other objects of the present invention will become apparent from the description contained herein.
In accordance with one aspect of the present invention, the foregoing and other objects are achieved by a method of nanometer-scale deposition of a metal onto a nanostructure including the steps of providing a substrate having thereon at least two electrically conductive nanostructures spaced no more than about 50 xcexcm apart; and depositing metal on at least one of the nanostructures by electric field-directed, programmable, pulsed electrolytic metal deposition.
In accordance with another aspect of the present invention, a method of nanometer-scale deposition of a metal onto a nanostructure includes the steps of providing a substrate having thereon at least two nanostructures having opposing tips spaced no more than 10 xcexcm apart so that an electric field is strongest between the tips to facilitate an electrolytic metal deposition reaction on at least one of the tips; and depositing metal on at least one of the tips by precisely controlling the amount of electrolytic metal deposition using a programmable pulsed current source to control the number of electrons used in the electrolytic deposition reaction to achieve a deposition rate in the range of 1500 to 1014 metal atoms per pulse.
In accordance with a further aspect of the present invention, a method of nanometer-scale depletion of a metal from a nanostructure includes the steps of: providing a substrate having thereon at least two electrically conductive nanostructures spaced no more than about 50 xcexcm apart, at least one of the nanostructures having a metal disposed thereon; and depleting at least a portion of the metal from the nanostructure by electric field-directed, programmable, pulsed electrolytic metal depletion.
In accordance with another aspect of the present invention, a method of nanometer-scale depletion of a metal from a nanostructure comprising the steps of: providing a substrate having thereon at least two nanostructures having opposing tips spaced no more than 10 xcexcm apart so that an electric field is strongest between the tips to facilitate an electrolytic metal depletion reaction from at least one of the tips, at least one of the tips having a metal disposed thereon; and depleting at least a portion of the metal from the tip by precisely controlling the amount of electrolytic metal depletion using a programmable pulsed current source to control the number of electrons used in the electrolytic depletion reaction to achieve a depletion rate in the range of 1500 to 1014 metal atoms per pulse.